Muhammad Ali all day. He was ridiculously balanced & light on his feet especially when taking into consideration he was a pretty decent sized heavyweight. Fluidity at its finest.

I got no bones to pick with anyone choosing Ali, he was amazingly graceful for such a big man. Pep however seems to waste less movement. Both are amazing though. Wish there was more footage of Benny Leonard and Joe Gans. It is said they moved around the ring like they were on wheels.